The present invention relates to network interfacing, and more particularly, to methods and systems for controlling transmission of data between network stations connected to a telephone line.
Local area networks use a network cable or other media to link stations on the network. Each local area network architecture uses a media access control (MAC) enabling network interface cards at each station to share access to the media.
Conventional local area network architectures use media access controllers operating according to half-duplex or full duplex Ethernet (ANSI/IEEE standard 802.3) protocol using a prescribed network medium, such as 10 BASE-T. Newer operating systems require that a network station to be able to detect the presence of the network. In an Ethernet 10 BASE-T environment, the network is detected by the transmission of a link pulse by the physical layer (PHY) transceiver. The periodic link pulse on the 10 BASE-T media is detected by a PHY receiver, which determines the presence of another network station transmitting on the network medium based on detection of the periodic link pulses. Hence, a PHY transceiver at Station A is able to detect the presence of Station B, without the transmission or reception of data packets, by the reception of link pulses on the 10 BASE-T medium from the PHY transmitter at Station B.
Efforts are underway to develop an architecture that enables computers to be linked together using conventional twisted pair telephone lines instead of established local area network media such as 10 BASE-T. Such an arrangement, referred to herein as a home network environment, provides the advantage that existing telephone wiring in a home may be used to implement a home network environment. However, telephone lines are inherently noisy due to spurious noise caused by electrical devices in the home, for example dimmer switches, transformers of home appliances, etc. In addition, the twisted pair telephone lines suffer from turn-on transients due to on-hook and off-hook and noise pulses from the standard POTS telephones, and electrical systems such as heating and air conditioning systems, etc.
An additional problem in telephone wiring networks is that the signal condition (i.e., shape) of a transmitted waveform depends largely on the wiring topology. Numerous branch connections in the twisted pair telephone line medium, as well as the different associated lengths of the branch connections, may cause multiple signal reflections on a transmitted network signal. Telephone wiring topology may cause the network signal from one network station to have a peak-to-peak voltage on the order of 10 to 20 millivolts, whereas network signals from another network station may have a value on the order of one to two volts. Hence, the amplitude and shape of a received pulse may be so distorted that recovery of a transmit clock or transmit data from the received pulse becomes substantially difficult.
In addition, any attempt to implement a network in a home network environment may suffer from the additional disadvantage of the necessity of constantly reconfiguring the associated communication drivers in the network stations, depending upon which physical layer transceiver a user is going to use. In particular, a user may have a network station that has a 10 BASE-T PHY transceiver and a home network transceiver. Normally, the user would need to open the network configuration settings in the network station operating system software, and change the port selection manually from 10 BASE-T to home network, or vice versa. The requirement for manually reconfiguring (i.e., selecting) the network port may be a substantial annoyance for a user, especially if the user is not intimately familiar with reconfiguring driver software.
In addition, a problem arises when using two or more available network ports for different physical layer transceivers in that not all the links may be active on a particular network port. For example, a network station may be configured for receiving two or more network ports, each port configured for communicating according to a different network protocol, such as 10 BASE-T, 100 BASE-T, etc. However, a user may be unaware if a certain link is not active, for example, if the network is down at a remote end. Hence, a user may need to manually reconfigure the driver software each time the network is turned on in order to determine the optimum physical layer transceiver to use for network communications.
There is a need for a network station having a plurality of physical layer transceivers for communication on respective network media to automatically select a port for a physical layer transceiver, without user intervention.
There is also a need for a network station that can select between a physical layer transceiver port for a home network environment and other physical layer transceivers supporting respective physical layer protocols such as 10 BASE-T or 100 BASE-T.
These and other needs are attained by the present invention, where each physical layer transceiver providing communication for a corresponding network medium having a prescribed media protocol is able to determine a link status for the corresponding network medium. The network station accesses the link status for a plurality of physical layer transceivers by a shared media independent interface, and selects one of the physical layer transceivers based on the corresponding link status for communication on the corresponding network medium.
According to one aspect of the present invention, a method in a network station of establishing a connection to a network includes connecting a plurality of physical layer transceivers to physical layer media having respective media protocols, each physical layer transceiver having a corresponding physical layer address, at least one of the physical layer transceivers configured for transmitting and receiving network signals via a telephone line medium. The method also includes determining in each of the physical layer transceivers a link status for the corresponding network medium, accessing the link status for the respective physical layer transceivers via a shared media independent interface providing communications between the physical layer transceivers and the network station, and selecting one of the physical layer transceivers based on the corresponding link status for communication on the corresponding network medium. Determining the link status in each physical layer transceiver enables the network station to determine which network links, including the telephone line medium, are available for network transmission. Moreover, the selecting of one of the physical layer transceivers enables a network station to automatically configure itself for network communications, without user intervention.
According to another aspect of the present invention, a network station configured for communication on a network includes a plurality of physical layer transceivers configured for determining the link status on respective network media, at least one of the network media being a telephone line medium. The network station also includes a media access controller configured for obtaining the link status for the respective physical layer transceivers via a shared media independent interface, and a controller for selecting one of the physical layer transceivers for network communication based on the obtained link status for the respective network media.
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.